3D Printing Multifunctional Hydrogels for Controlled Vapor Release

Multifunctional and biocompatible soft hydrogels have the ability to encapsulate large water content. In particular, the stimuli-responsive hydrogels abruptly undergoing to the volumetric changes in response to temperature and magnetic field have many applications in water-energy and biomedical fields. Herein, we propose a novel strategy to additively fabricate photocurable thermoresponsive p(NIPAm-co-PEGDA) hydrogel device with controlled moisture-release functionality. Our experimental results indicate that by changing the monomer/crosslinker/solvent ratio and manipulating the crosslinking density, micro-3D printed hydrogel structures with pores below 100 nm behave as nano-valves to release the trapped water. The intrinsic water retention property and wettability modulation from hydrophilicity to hydrophobicity upon heating play critical roles in controlling vapor release of 3D printed p(NIPAm-co-PEGDA) hydrogels. Therefore, the vapor release behavior is investigated for various formulations of p(NIPAm-co-PEGDA) hydrogel at different temperatures (25-50^oC) and levels of relative humidity (40-100%). The varied crosslinking density of hydrogels during 3D printing is characterized to tune the vapor release kinetics upon heating. These functional 3D printed biocompatible hydrogel structures have wide applications in water and biomedical fields, where controlled vapor/nutrients/drug release is the key.